Microwave-sensing device are used for measuring distances in a plurality of industrial applications. Often, it is necessary, for example, to measure the fill level of a medium, such as a liquid or a bulk material in a container. For this purpose, fill level measuring devices are used that often contain a microwave-sending device of the aforementioned kind, wherein the fill level is derived from the measured distance between the microwave-sending device arranged in the space above the medium and the surface of the medium.
In the microwave-sending device, electronics generate microwaves, a wave coupler couples the generated microwaves in the waveguide, and a waveguide guides the coupled microwaves to the wave-emitting section, in which the guided waves are converted to free waves. The free waves are emitted substantially directed toward the medium and reflected back from the surface of the medium toward the fill level measuring device. The microwave-sending device usually also serves as a microwave receiver that calculates the distance to the medium according to a known radar method. Often, the microwave-sending device also derives the fill level from the calculated distance. Of course, microwave-sending devices can be used not only in fill level measuring devices, but also in any measuring device that determines the distance between the microwave-sending device and a surface using one of the known radar methods. Nevertheless, a fill level measuring device or a microwave-sending device for such a fill level measuring device will be discussed here.
A microwave sender for a fill level measuring device that makes a radar-based determination of the fill level of a medium in a container having electronics, an antenna and a housing is known from International Patent Application Publication WO 03/085365 A1 and corresponding U.S. Pat. No. 7,075,480. The electronics and the antenna are located in a hollow of a housing and the hollow is sealed, at least in respect to the atmosphere of the container in which the housing is found. Due to this structure, the electronics and the antenna are protected against aggressive conditions and against chemical and mechanical effects.
German Patent Application DE 10 2011 010 801 is directed to a microwave-sending device for emitting microwaves for a fill level measuring device with electronics, a wave coupler, a waveguide and a housing. The electronics, the wave coupler, and the waveguide are arranged inside the housing. Hollows in the housing and the structures guiding the microwaves are completely filled with a dielectric casting, so that the propagation of the microwaves takes place in the casting. Due to the propagation of the microwaves in the casting, as opposed to free space, the minimum size of the structures guiding the microwaves, such as the waveguide, is reduced. The electronics, the wave coupler, and the waveguide are affixed to the housing appropriate fixtures. Due to the casting of the electronics and the waveguide, mechanical robustness against shocks and vibrations that occur in mechanically harsh environments is increased.
Microwave-sending devices known from the prior art have a housing and fixtures for components such as electronics, a wave coupler, and a waveguide, wherein the fixtures affix and align the components to the housing as well as to each other. Additionally, a closure for the housing with a seal and a fixture for affixing to the housing are necessary so that the components can be protected against environmental effects, (e.g., according to DIN EN 60529 IP68) by the closed housing after being inserted and affixed in the housing. The fixtures for the components, and the closure having the seal and the fixture, increase the constructional complexity as well as the production and assembly effort, which then increase costs.